You sure can:
Uninstall Windows XP Professional
For systems upgraded to Windows XP Professional from Windows 98 or Windows Me, you might be able to revert to the previous operating system as a method for resolving the following problem.
After upgrading to Windows XP Professional, you might discover that a critical application does not run or a device fails to initialize. Consult the software or hardware manufacturer to determine if a compatibility problem exists. You might also learn that one of the following conditions applies to you:
The program does not run correctly, even after running the Program Compatibility Wizard. For more information, see "Program Compatibility Wizard" earlier in this appendix.
The manufacturer no longer supports the application or device and an update is not available. Furthermore, device drivers for earlier versions of Windows do not work.
The manufacturer supports the device, but a Windows XP Professional update is not yet available. Furthermore, device drivers for earlier versions of Windows do not work.
Reverting to the previous operating system enables you to continue using the application or device while waiting for a compatible update or replacement. You can choose to upgrade to Windows XP Professional at a later date.
To uninstall Windows XP Professional
In the Run dialog box, type appwiz.cpl, and then click OK.
In the Currently installed programs box, click Windows XP Professional, and then click Remove.
Follow the on-screen instructions to uninstall Windows XP Professional.
You can only uninstall Windows XP Professional if your computer meets all of the following requirements:
The computer was upgraded from Windows 98 or Windows Me.
The system partition uses the FAT or FAT32 file system. This is the default for computers upgraded from Windows 98 and Windows Me. If you use Convert.exe to convert the file system from FAT to NTFS, you can no longer uninstall Windows XP Professional.
The computer had sufficient disk space to save uninstall information when you upgraded to Windows XP Professional.
To detect incompatible components before upgrading to Windows XP Professional, run Setup with the /checkupgradeonly parameter.
To check system compatibility before installing Windows XP Professional
Insert the Windows XP Professional operating system CD into the computer, and then wait for the Welcome to Microsoft Windows XP screen to appear. Click Check system compatibility.
– or –
At the command prompt, type drive:\i386\winnt32.exe /checkupgradeonly (where drive: represents the network or CD-ROM path to the Windows XP Professional installation files